Influence of Reheating Method and Water Content on Change of the Physicochemical Properties of Retrograded Rice Starch

The effect of the reheating method (microwave, autoclave and steam) and water content (65, 75, 85 and 95%) on change of the physicochemical properties of retrograded rice starch was investigated. The increment of gelatinization after heat treatment in the autoclave was the highest (44.9% at 95% water content), and it also showed an increasing trend regardless of reheating methods as the water content was increased from 65% to 95%. The water-holding capacity (WHC) of the retrograded rice starch was increased compared to that of control after reheating regardless of reheating method and water content, and the maximum value (33.2%, w/v) was observed in the sample reheated with steam at a water content of 95%. The retrograded rice starch reheated in the autoclave showed a decreased peak viscosity, breakdown, final viscosity and setback. In particular, these parameters were lowest in samples reheated in an autoclave. Also, in the autoclaved samples the crystallinity of retrograded rice starch decreased as the water content increased. The microstructure of the reheated samples was filamentous type composed of numerous small cavities.